The emissions benefit in catalytically treating internal combustion engine exhaust gas, such as by passing the exhaust gas through a catalytic converter, is generally accepted. Generally, the catalyst used in such converters is able to purify pollutants in the exhaust gas only when the temperature of the catalyst becomes higher than a certain temperature, i.e., the catalyst in the converter does not work when the temperature is lower than the activation temperature of the catalyst.
Usually, the catalyst in the converter is gradually heated by the exhaust gas and reaches the activation temperature after the engine starts (commonly referred to as “light-off” temperature). However, when the temperature of the engine is low, for example, after a cold start of the engine, it takes a long time to heat the catalyst to the light-off temperature since the heat of the exhaust gas is removed by the cold wall of the exhaust passage before it reaches the converter. Therefore, the exhaust gas of the engine is not sufficiently purified during the period where the temperature of the catalyst is lower than the light-off temperature. In some cases, it may take several minutes before the catalyst begins to work during which time exhaust gas pollutants are emitted into the environment.
To improve the efficiency of the catalytic converters, heating devices were introduced inside the converter assemblies. The heating devices become energized just after the engine is started, bringing the catalyst up to its light-off temperature sooner allowing for faster and increased emissions purification to occur during cold start.
Traditional heating devices in catalytic converters are basically used to apply heating to the entire catalyst front face or the entire catalyst body. Although both of these methods of heating the catalyst are known to demonstrate faster and increased emissions purification during cold start in comparison to non-heated converter assemblies, there is still some period between cold start and the catalyst reaching light-off temperature where emissions purification is not occurring. The following exemplary embodiments seek to further address the emissions purification limitations between engine cold start and when the catalyst attains light-off temperature.